Excess sludge coupling treatment method

Abstract

The invention discloses a residual sludge coupling treatment method, belongs to the technical field of residual sludge treatment, and solves the problem that the sludge treatment efficiency is limited due to the fact that the existing residual sludge treatment method based on ultrasonic coupling alkali does not ensure the sludge activity to the maximum extent. According to the method, dynamic coupling optimization among the parameters is realized by establishing a mathematical relationship among the carbon source release amount, the specific aerobic rate and the operation parameters, and based on multi-objective optimization, the ultrasonic energy consumption is further reduced, and the optimal pH value is obtained, that is, the optimal solution for simultaneously improving the carbon source release amount and the sludge activity is obtained, and the method is suitable for industrial production. And for subsequent sludge in-situ recycling, not only is the sludge yield reduced, but also the treatment efficiency of a biochemical system is improved.

Description

Technical Field

[0001] The invention relates to the technical field of excess sludge treatment, and in particular to an excess sludge coupling treatment method. Background Art

[0002] At present, common methods for decomposing residual sludge include oxidation, alkaline treatment, ultrasonic treatment, heat treatment, etc. Physical treatment methods based on heat, microwaves and ultrasound have high energy consumption, acid-base treatment, chemical oxidation and other drugs consume a lot, are easy to corrode equipment, have high carbon emissions and may cause secondary pollution. The treatment method of lysozyme is costly and its stability needs to be verified. Among these methods, ultrasonic technology has been applied in actual engineering. This technology achieves effective decomposition of sludge through cavitation effect, promotes the release of organic matter to supplement carbon source for utilization, and creates conditions for the next step of utilization. However, ultrasound has high power during the treatment process and often requires a high energy density input. It has the characteristics of high operating energy consumption and short device service life, which greatly limits its further promotion and application.

[0003] In order to solve this problem, the prior art usually uses an alkaline environment to improve the cell wall breaking efficiency of ultrasound, thereby improving the utilization rate of ultrasound. However, the prior art does not consider the relationship between ultrasound density, pH value of the alkaline environment, carbon source release and sludge activity, and usually only roughly maintains the pH value at a certain higher value. For example, the invention patent with announcement number CN111646663B discloses a process for breaking sludge by hydraulic cavitation, which adjusts the pH value to 11 or 12. Although it improves the utilization rate of ultrasound, promotes the release of carbon source, and ensures the activity of sludge to a certain extent, the pH value and ultrasonic energy consumption value are roughly set and are not optimized to improve the sludge activity, thereby limiting the treatment efficiency of the residual sludge. Summary of the invention

[0004] In view of the above problems in the prior art, the present invention provides a residual sludge coupling treatment method, which solves the problem that the existing residual sludge treatment method based on ultrasonic coupling alkali does not maximize the sludge activity, thereby limiting the sludge treatment efficiency.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for coupled treatment of excess sludge is provided, comprising the steps of:

[0007] S1. Obtain the relationship between the carbon source release amount, specific aerobic rate, pH value and ultrasonic energy density in the residual sludge;

[0008] S2. Determine a threshold of carbon source release according to the carbon source demand of the excess sludge, and constrain the carbon source release to be greater than the threshold, establish an objective function for maximizing the specific aerobic rate and minimizing the ultrasonic energy density according to the relationship, and solve the maximum value of the objective function to obtain the optimal pH value and the optimal ultrasonic energy density value;

[0009] S3. The excess sludge is coupled and treated synchronously according to the optimal pH value and the optimal ultrasonic energy density value.

[0010] In this scheme, by establishing a mathematical relationship between the carbon source release, specific aerobic rate and operating parameters, dynamic coupling optimization between parameters is achieved, and the optimal pH value is obtained based on multi-objective optimization to maximize sludge activity and minimize ultrasonic energy density. Under the premise of ensuring the carbon source release demand, not only the sludge yield is reduced, but also the energy utilization efficiency and sludge treatment efficiency are significantly improved.

[0011] Furthermore, the relational expression in step S1 is:

[0012]

[0013] SOUR=-129.78+89.22·b-2147.88·b 2 +18632.61 b 3 -68286.24 b 4

[0014] +89519.73 b 5 -14.02·ln(10 -a )-0.33·[ln(10 -a )] 2

[0015] Among them, S COD is the carbon source release; SOUR is the specific aerobic rate; a is the pH value, and b is the ultrasonic energy density.

[0016] In this scheme, 10 -ais the concentration of hydrogen ions, which can be directly obtained by measuring the concentration of hydrogen ions, which is more accurate. The polynomial logarithmic mixed equation structure can accurately characterize the exponential decay characteristics of SOUR under pH values, and reduces the prediction error compared to the linear model. SOUR represents the utilization efficiency of dissolved oxygen by microorganisms in sludge, which can be used to characterize sludge activity. The larger the SOUR, the higher the activity of sludge. The relationship shows that when the pH is less than 10, alkali stimulates cells to secrete more extracellular polymers. As SOUR gradually increases, when the pH is greater than 10, the dissolution of extracellular polymers by alkali is further aggravated, and even lyses the cells, thereby releasing more organic matter. However, at this time, SOUR decreases slightly, but compared with the untreated residual sludge, the activity is still in an enhanced state. SOUR increases first and then decreases with the increase of ultrasonic sound energy density, which means that low-density ultrasound can not only promote the release of organic matter in sludge, but also enhance the activity of sludge. The relationship shows that the residual sludge can simultaneously achieve COD release and improved activity of the treated sludge under milder alkaline environmental conditions, solving the previous problem of releasing intracellular carbon sources through the sludge crushing process accompanied by reduced sludge activity.

[0017] Furthermore, the objective function C of step S2 is: C=w1SOUR-w2·b, where w1 and w2 are the weights of SOUR and b respectively. The weight setting can be selected to focus on sludge treatment efficiency or ultrasonic energy consumption according to actual conditions, which is more in line with actual production needs.

[0018] Furthermore, the solution method of step S2 is: construct the Lagrangian function and confirm The constraints of , and combined with the boundary conditions, the optimal pH value and the optimal ultrasonic energy density value are obtained, where:

[0019]

[0020] The constraints are:

[0021]

[0022] in, is the Lagrangian function of pH value a, ultrasonic energy density b and Lagrangian multiplier λ; SCOD min is the threshold value.

[0023] In this scheme, the rigid requirement of ensuring that the carbon source release amount is greater than the threshold is ensured to avoid the risk of insufficient carbon source caused by the traditional trial and error method.

[0024] Furthermore, the Lagrangian function The boundary conditions also include: the ultrasonic energy density b ranges from 0 to 0.1 W / mL, which narrows the ultrasonic range of low-density ultrasound and further reduces ultrasonic energy consumption.

[0025] Furthermore, the Lagrangian function The boundary conditions also include: pH value a ranges from 9 to 11. The extreme pH conditions are avoided.

[0026] The invention discloses a method for coupling treatment of excess sludge, which has the following beneficial effects:

[0027] 1. The present invention realizes dynamic coupling optimization among parameters by establishing a mathematical relationship among carbon source release, specific aerobic rate and operating parameters, and based on a multi-objective optimization method, not only the ultrasonic energy consumption is further reduced, but also the optimal pH value is obtained, that is, the optimal solution for simultaneously improving the carbon source release and the sludge activity is obtained. For the subsequent in-situ resource utilization of sludge, not only the sludge yield is reduced, but also the treatment efficiency of the biochemical system is improved.

[0028] 2. The relationship of the present invention shows that when the residual sludge is in a milder alkaline environment and the pH value is less than 11 and close to 10, COD release and activity improvement of the treated sludge can be achieved simultaneously, which solves the problem of releasing intracellular carbon source through the sludge crushing process accompanied by reduced sludge activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of the excess sludge coupling treatment method. DETAILED DESCRIPTION

[0030] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0031] The prior art does not consider the relationship between ultrasonic wave density, pH value of alkaline environment, carbon source release and sludge activity. It usually just roughly maintains the pH value at a certain higher value, and basically sets it at 11 or above 11. Although the utilization rate of ultrasonic waves is improved, the release of carbon sources is promoted, and the activity of sludge is guaranteed to a certain extent, the pH value and ultrasonic wave energy consumption value are roughly set and not optimized to improve sludge activity, thus limiting the treatment efficiency of residual sludge. In order to solve this problem, the present application provides a method for coupling treatment of residual sludge, which realizes dynamic coupling optimization between parameters by establishing a mathematical relationship between carbon source release, specific aerobic rate and operating parameters, and obtains the optimal solution for simultaneously improving carbon source release and sludge activity based on a multi-objective optimization method, that is, the optimal pH value, which not only maximizes the treatment efficiency of the biochemical system, but also shows that the optimal pH value is less than 11, breaking the conventional pH value setting.

[0032] refer to Figure 1 , a method for coupling treatment of excess sludge, comprising the steps of:

[0033] S1. Obtain the relationship between the carbon source release amount, specific aerobic rate, pH value and ultrasonic energy density in the residual sludge.

[0034] The relationship in step S1 includes:

[0035]

[0036] Among them, S COD is the carbon source release, which expresses the relationship between the COD concentration of the sludge supernatant after residual sludge treatment and the ultrasonic energy density and pH within the low-density ultrasonic range, and the unit is mg / L; a is the pH value, and b is the ultrasonic energy density, ranging from 0-0.3W / mL.

[0037] The COD concentration of the treated sludge supernatant first increases and then gradually stabilizes with the increase of ultrasonic energy density, and the greater the pH, the greater the slope of the COD concentration increase trend with the increase of ultrasonic energy density. Therefore, the range of ultrasonic acoustic energy density can be narrowed to (0-0.1W / mL), and the ultrasonic acoustic energy density can be further reduced, thereby reducing ultrasonic energy consumption. In addition, the stimulation of lower pH (9-11) and low-density ultrasound can not only release organic matter in sludge flocs, but also increase the activity of sludge. The relationship between the specific aerobic rate (SOUR) of treated sludge and ultrasound and pH is as follows:

[0038] SOUR=-129.78+89.22·b-2147.88·b 2 +18632.61 b 3 -68286.24 b 4

[0039] +89519.73 b 5 -14.02·ln(10 -a )-0.33·[ln(10 -a )] 2

[0040] Among them, SOUR is the specific aerobic rate, and the unit is mgO2 / gSS·h. This relationship shows that when the pH is less than 10, alkali stimulates cells to secrete more extracellular polymers, and SOUR gradually increases. When the pH is greater than 10, the alkali further intensifies the dissolution of extracellular polymers, and even lyses the cells, thereby releasing more organic matter. However, at this time, SOUR shows a slight decrease, but compared with the untreated residual sludge, the activity is still in an enhanced state. SOUR first increases and then decreases with the increase of ultrasonic sound energy density, which means that low-density ultrasound can not only promote the release of organic matter in sludge, but also enhance the activity of sludge.

[0041] S2. Determine the threshold of carbon source release according to the carbon source demand of the residual sludge, and constrain the carbon source release to be greater than the threshold. According to the relationship, establish an objective function for maximizing the specific aerobic rate and minimizing the ultrasonic energy density. Solve the maximum value of the objective function to obtain the optimal pH value and the optimal ultrasonic energy density value.

[0042] The objective function C of step S2 is: C=w1SOUR-w2·b, where w1 and w2 are the weights of SOUR and b respectively. The weight setting can be selected to focus on sludge treatment efficiency or ultrasonic energy consumption according to actual conditions, which is more in line with actual production needs.

[0043] The solution method of step S2 can be a genetic algorithm or a multi-objective optimization algorithm. Specifically, this solution constructs a Lagrangian function and confirm The constraints of , and combined with the boundary conditions, the optimal pH value and the optimal ultrasonic energy density value are obtained, where:

[0044]

[0045] The expressions of constraints and boundary conditions are:

[0046]

[0047] in, is the Lagrangian function of pH value a, ultrasonic energy density b and Lagrangian multiplier λ; SCOD min is the threshold value.

[0048] S3. The excess sludge is coupled and treated synchronously according to the optimal pH value and the optimal ultrasonic energy density value.

[0049] Although the specific implementation of the invention is described in detail in conjunction with the drawings, it should not be understood as limiting the scope of protection of this patent. Within the scope described in the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A method for coupling treatment of excess sludge, characterized in that: Includes steps: S1. Obtain the relationship between the carbon source release amount, specific aerobic rate, pH value and ultrasonic energy density in the residual sludge; S2. Determine a threshold of carbon source release according to the carbon source demand of the excess sludge, and constrain the carbon source release to be greater than the threshold, establish an objective function for maximizing the specific aerobic rate and minimizing the ultrasonic energy density according to the relationship, and solve the maximum value of the objective function to obtain the optimal pH value and the optimal ultrasonic energy density value; S3. The residual sludge is coupled and treated synchronously according to the optimal pH value and the optimal ultrasonic energy density value.

2. The excess sludge coupling treatment method according to claim 1 is characterized in that: The relationship in step S1 is: SOUR=-129.78+89.22·b-2147.88·b 2 +18632.61·b 3 -68286.24·b 4 +89519.73·b 5 -14.02·ln(10 -a )-0.33·[ln(10 -a )] 2 Among them, S COD is the carbon source release; SOUR is the specific aerobic rate; a is the pH value, and b is the ultrasonic energy density.

3. The excess sludge coupling treatment method according to claim 2 is characterized in that: The objective function C of step S2 is: C=w1SOUR-w2·b, where w1 and w2 are the weights of SOUR and b respectively.

4. The excess sludge coupling treatment method according to claim 3 is characterized in that: The solution method of step S2 is: construct the Lagrangian function and confirm The constraints of , and combined with the boundary conditions, the optimal pH value and the optimal ultrasonic energy density value are obtained, where: The constraints are: in, is the Lagrangian function of pH value a, ultrasonic energy density b and Lagrangian multiplier λ; SCOD min is the threshold value.

5. The excess sludge coupling treatment method according to claim 4 is characterized in that: Lagrangian function The boundary conditions include: the ultrasonic energy density b ranges from 0 to 0.1 W / mL.

6. The excess sludge coupling treatment method according to claim 5 is characterized in that: Lagrangian function The boundary conditions include: pH value a ranges from 9 to 11.

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